Recombinant expression in bacterial, yeast, insect, plant or mammalian cells is fundamental for the production of proteins that are used for research as well as therapeutic applications. Recently, the yield of recombinant protein expression in Chinese Hamster Ovary (CHO) cells has been significantly enhanced by optimizing multiple parameters such as culture medium composition, fermentation parameters, as well as optimization of the constructs that are used to drive the expression of the gene encoding the recombinant protein of interest.
Some proteins are composed of several polypeptides that can associate in complexes that can be covalently or non-covalently linked. Antibodies are an example of such a class of proteins as they are composed of four polypeptides (i.e. two heavy chains and two light chains) that are linked by disulfide bonds. Due to their commercial and therapeutic importance, the expression of antibodies in CHO cells has been the subject of intense efforts of optimization, aiming at maximizing the expression of the two chains that compose the antibody. However, major differences can be observed as the levels of expression can vary up to 200-fold between antibodies.
Previous optimization approaches aimed at increasing the expression levels of polypeptides in order to achieve higher production yields. In the case of protein complexes composed of multiple polypeptides, unbalanced expression can limit assembly of the desired molecule, promote production of unwanted products and limit the overall production yield. Accordingly, there exists a need for methods for improving expression of protein complexes.